Researchers Boning Up on Stem Cells

The concept sounds like it’s straight out of the science fiction that Dr. Elizabeth Loboa loves to read and watch so much. Take stem cells from discarded fat and create bones from them. Yet, the assistant professor in the Department of Biomedical Engineering is producing real bone cells in her lab, hoping to one day provide body parts to wounded soldiers, help children with skeletal birth defects, or treat an aging population dealing with osteoporosis.

Loboa places the adult stem cells in devices that tug or twist them repeatedly until they start differentiating into bone cells and producing the proteins found in natural bone. The tension, compression, and shear forces mimic the stresses the stem cells undergo in the human body, says Loboa, a mechanical engineer whose interest in stem cells grew out of computer simulations she developed to measure tissue regeneration and growth under various mechanical loads. “Our bodies provide mechanical, chemical, and electrical cues,” she says, “to give stem cells an idea of how they should differentiate into various types of cells.”

Drs. Laura Clarke and Russell Gorga have teamed up with Loboa to see if they can replicate the electrical cues and accelerate the process of creating bone cells. Gorga, an assistant professor in the College of Textiles (COT) who specializes in polymer physics, builds tiny “scaffolds” of nonwoven fibers that allow the stem cells to grow in more of a 3-D setting than a culture dish provides.
He and COT graduate Seth McCullen, now a Ph.D. student in Loboa’s lab, came up with the idea of adding carbon nanotubes to a biodegradable polymer as it’s sprayed into a web, making the resulting scaffold stronger and electrically conductive.

Adult stem cells from fat are placed in devices that tug or twist them repeatedly until they start differentiating into bone cells.

Clarke, a physicist in the College of Physical and Mathematical Sciences, then applies an alternating current of about 10 volts per centimeter to the scaffolds and stem cells. Clinical tests have shown such electrical pulses help bone fractures heal more quickly, she says. The team’s experiments have shown bursts of calcium release resulting from the oscillating current. “The electric fields put the stem cells under stress,” Clarke says. “All we’re trying to do is trigger a natural response to the cell’s surroundings.”

Loboa harvests the stem cells from fat extracted from patients undergoing liposuction at UNC Hospitals in Chapel Hill. Such a universal source could make it easier to build bones for individual patients that their bodies wouldn’t reject, she says. “We’re basically recycling waste tissue,” she says. “The adult stem cells also might be able to regenerate cartilage, ligaments, and muscle tissue.” Science fiction is quickly becoming reality.

Fat-derived stem cells that have been stained purple can be seen growing rapidly on scaffolds of nonwoven polylactic acid fibers over a 24-hour period. The scaffold on the right, which has been oxygen plasma treated, causes more stem cell growth and proliferation than the untreated scaffold at left.